'controllable' radiator in the conservatory

I'd like to run a spur off our central heating to add a radiator in the conservatory. As the doors seperating the conservatory will be left open most of the time, i'd like to heat it alongside the living room rather than leaving the 2 rads in the living room to heat the conservatory too.

However, I know there are some regulations regarding heating conservatories and have found out that if you install a rad in the conservatory it needs to be 'controllable' - what on earth does that mean? Obviously it'll have valves fitted to it, and it will run off of the same central heating curcuit as the rest of the house, so when the thermostat in the living trips out, the heating in the conservatory will also stop. Is this where the problem lies - a conservatory is inevitably always going to be colder than a living room becuase thats where the stat is placed?

Any help much appreciated...

T.hermostatic R.adiator V.alve

will that make any difference if the conservatory is the coldest room and its all run off the same system? The stat will have already shut the boiler down long before the TRV gets to the same temp as the rest of the house wouldn't it..?

Even if I set the room stat to 20C and the TRV to 25C, the conservatory is only ever realisticall going to reach 20C?

The system should be designed and radiators sized so that each room (in theory) reaches its design temperature.
Can be difficult in a conservatory with a lot of glass or poly roof but thats how it should work.

Or to put it more bluntly - wack a ******* big radiator (with TRV) in the conservatory so that it gets stands a chance of getting up to temperature before (or at the same time as) the rest of the house.

Of course once the stat has shut the heating off the more difficult problem is that the conservatory will cool quicker, but you did say you were leaving the doors open most of the time, so the conservatory will cool the living area and cause the heating to come back on in time.

I suppose (aside from upgrading the system throughout to TRVs) a neat trick would be a auxillary electric heater set at 20C that is wired via a relay so it it only comes on if the heating is turned on but the thermostat in the living area is indicating above 20C.